ABS resin is widely used for the production of automobile interior parts due to its superior mechanical properties, heat resistance, and moldability.
However, with vibration during car driving, when automobile interior parts made of ABS resin come into contact with and rub against each other or such a part comes into contact with and rubs against another part such as a lining sheet or a foam made of polyvinyl chloride, chloroprene rubber, polyurethane, natural rubber, polyester, or polyethylene, squeaking noises (rubbing noises) may be generated. For example, in a ventilator made of ABS resin is installed a valve shutter using a chloroprene rubber foam or the like as a sealing material in order to adjust an air quantity. If the valve shutter is rotated for air quantity adjustment, a case of the ventilator made of the ABS resin rubs against another member e.g., a case of the sealing material, so that squeaking noises may be generated.
Moreover, since ABS resin and ASA resin are amorphous resins, they are higher in coefficient of friction as compared with crystalline resins such as polyethylene, polypropylene and polyacetal, and it is well known that, like an air outlet of an air conditioner in an automobile or buttons of a car audio system, when fitting with a member made of another resin, a stick slip phenomenon as illustrated in FIG. 1 occurs to generate squeaking noises because of a large coefficient of friction. The stick slip phenomenon is a phenomenon that is generated when two objects rub against each other. When an object M connected with a spring is placed on a driving table that moves at a driving speed V as illustrated by a model of FIG. 2(a), the object M moves toward the right direction first as illustrated in FIG. 2(b) together with the table moving at the driving speed V by the action of a static frictional force. When the force by which the object M is to be restored to its original position becomes equal to the static frictional force, the object M starts to slip in the opposite direction to the driving speed V. At this time, the object M comes to receive a kinematic frictional force, and the slip is stopped when the force of the spring becomes equal to the kinematic frictional force as illustrated in FIG. 2(c), so that the object M comes again into a state where it attaches on the driving table and it moves again in the same direction as the driving speed V (FIG. 2(d)). A stick slip phenomenon refers to a phenomenon that when making an object slip as described above, the object repeats sticking and slipping, and the object M receives a time-varying load as illustrated in FIG. 1. It has been argued that if the difference Δμ between the coefficient of static friction μs of FIG. 1 (at the time of FIG. 2 (b)) and the lower end of a saw wavy form μl (at the time of FIG. 2 (c)) is large, squeaking noises are generated easily. A dynamic friction coefficient is a middle value between μs and μl.
Such a squeaking noise is a major cause that spoils comfortableness and silence when riding a car, and therefore reduction of squeaking noises is demanded strongly.
On the other hand, it is known that the stick slip phenomenon occurs remarkably when the friction velocity dependency of a coefficient of friction determined on the basis of the Amonton-Coulomb's law takes a negative value (see non-patent document 1), and it is possible to inhibit the occurrence of the stick slip phenomenon and reduce the generation of squeaking noises by bringing the friction velocity dependency of the coefficient of friction close to zero or by adjusting it to a positive value greater than zero.
Then, in order to prevent such squeaking noises, a method of applying Teflon (registered trademark) coating to the surface of a member, a method of mounting a Teflon (registered trademark) tape, a method of applying a silicone oil, etc. have been performed. However, the step of mounting or applying is very complicated and requires time and effort, and there is a problem that the effect does not continue when being placed under high temperatures for a long time.
As a method for changing the properties of the material to be used for an automobile interior part, a method of incorporating a silicone oil into an ABS resin and a method of incorporating an epoxy-containing olefin copolymer into an ABS resin have been proposed. For example, there have been disclosed a technology of incorporating an organosilicon compound into a resin composed of a polycarbonate resin and an ABS resin (see patent document 1), a technology of incorporating a flame retardant, a flame retarding aid and a silicone oil into an ABS resin (see patent document 2), a technology of incorporating a silicone oil into an ABS resin, an MBS resin, and a HIPS (high impact polystyrene) resin (see patent document 3), a technology of incorporating an alkane sulfonate surfactant into an ABS resin (see patent document 4), and a technology of incorporating a modified polyorganosiloxane having at least one reactive group selected from among an epoxy group, a carboxyl group and an acid anhydride group into an ABS resin to increase water repellency and using the same as a wet area part in a bathroom or toilet (see patent document 5).
However, an effect of reducing squeaking noises obtained by these methods is not sufficient. Even if the effect of preventing squeaking noises is considerably exhibited just after molding, the durability of the effect is poor, and in particular, there is a problem that the effect deteriorates remarkably when being placed under high temperatures for a long time.